I also had , 5.5 hours worth of PROBLEMS trying to install NIS2007, out of the box, on my HP computer which came with Vista and NIS2006 trial. The two other XP computers had no problems.
The problem was solved for me by:
1. Downloading & Using the Norton Removal Tool @ http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2005033108162039
2. Downloading the free trial version of NIS2007 @ http://shop.symantecstore.com/servlet/ControllerServlet?Action=DisplayPage&Env=BASE&Locale=en_US&SiteID=symnahho&id=ProductDetailsTrialPage&productID=59771600
3. Install this version using the Key Code that came with the Retail version that you paid for.

I hope this Helps someone!
4. Download & install the Add ?On Pack if you want it @ http://www.symantec.com/home_homeoffice/support/special/upgrade2007/vista/migration_start.jsp